package com.dateConstruction._04_seqStack;

public interface Stack<T> {
    
    public abstract boolean isEmpty();
    // 元素x入栈
    public abstract void push(T x);
    // 返回栈顶元素，未出栈
    public abstract T peek();
    // 出栈，返回栈顶元素
    public abstract T pop();
}
